dashboard refreshes slowly (~30 sec), though it is based on a report that refreshes quickly (couple of seconds) when running it alone.

Details:

Dashboard consists of a single table with 3 columns in it. Source for this table is a report that based on data sent by third-party app. There are only about 30 rows of data for this report. When I click "Run report" it refreshes quickly, but when I click "Refresh dashboard", it may take about 30 seconds to refresh.

Has anyone encountered this issue? What can be done to improve dashboard performance?